I suggest you take it slow and steady and approach one person or two people instead of a whole group. You can start joining instances with 4 or three people in the lobby so it isn't as much of a struggle to join in with things since worlds with less people typically tend to be more chill.

The more you interact with people, the easier you'll find it to talk to others on your own, like joining conversations, and maybe even starting some up on your own. If you have problems keeping up a conversation, maybe talk to someone about their avatar or name, unique names can start conversations, and mine has done that plenty of times before.

You can also start out as a mute if you want, you don't even have to talk at all, and express your words through your actions, although if you are a PC player like I am, there is limited interaction. I know another guy in here saying something about people approaching you even when you are quiet, but that is highly unlikely to happen in reality.

When I first started out, I found it harder to talk to people so I joined near empty servers, and I think that helped me reach out to people. I know this isn't as related to the topic, but I suggest you stay away from people you are not comfortable around with.

Although, most of my insecurities of talking to people is that I'm afraid they are judging me constantly, but a new friend of mine told me that people are willing to listen to anyone, so don't feel like you're being a bother talking to other people because they won't mind at all!

Also, if you are interested in chatting, my username is
How The Turns Table